Session API primitives for governed external control (create-only, expected-seq, dispose)

[hagaseinstitute]

We embed DeepSeek Harness (dsh-v0.2.0-rc.2, commit 639ed01) behind a governed sidecar that must create and control development sessions on behalf of authenticated tenants. Reviewing the @Remote surface in packages/api/session-controller and packages/api/workspace-controller, we cannot build a bounded, reversible lifecycle today. We would like to propose four small, additive primitives:

1. Create-only mode for session.create. Today an explicit sessionId adopts an existing live or persisted session (commands.ts "create or idempotently adopt"). Proposal: optional mode: 'create-only' that fails with session/already-exists instead of adopting.
2. Expected-state precondition on mutations. session.projections already returns asOfSeq. Proposal: optional expectedSeq on session.rename, session.cancel and workspace.archiveSession, failing with session/seq-conflict when the session advanced.
3. Bounded teardown. There is no external delete or dispose for a session. Proposal: session.dispose for a session with no history beyond creation (or behind a confirm flag otherwise), so a created-but-unused session can be removed.
4. Target-only archive responses. archiveSession / unarchiveSession return every archived session id. Proposal: an option to return only the target's state.

A principal-scoped credential at the /api boundary would complete the picture, but we understand api-request-trust.ts is intentionally not an auth layer; items 1–4 are useful independently.

We are happy to share more detail on the use case and to test any implementation against our sidecar.

[Chen-Lim]

Love this idea!
I actually built a similar workflow for my NuPhy Air V3 keyboard. My approach was to write a Cordis plugin inside DeepSeek Harness that exposes a native JSON-RPC server for external peripherals. By adapting my NuPhy Air V3 to communicate with this JSON-RPC interface, the keyboard can pull real-time DSH session states (like tool approval prompts or running status) and lets me do one-key jump and control—instantly focusing the target session and approving/aborting actions right from the keyboard. Building it as a Cordis + JSON-RPC plugin keeps the hardware adapter completely decoupled from the DSH client UI.